JP2010006927A - Surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protective film capable of being made to a wound superposed body or the like even when a soft adhesive agent is used, capable of easily peeling off an adhesive layer from a back surface of a base material even if the adhesive layer is adhered to a surface at an opposite side to a side of the base material where the adhesive layer is provided and capable of reasonably developing the wound superposed body. <P>SOLUTION: In the surface protective film, the adhesive layer containing a rubber based resin component (X) and an adhesion giving resin (Y) is superposed on the polyolefin based base material. In the surface protective film, surface roughness Ra of the adhesive layer is 2-8 μm, a surface projection interval Sm is 25-50 μm, and the surface or the outermost layer of the polyolefin based base material at the side of the surface protective film where the adhesive layer is not superposed is subjected to friction treatment. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a surface protective film used to prevent adhesion of dust to the surface of an adherend and damage to the surface of the adherend, and more specifically, even when a soft adhesive is used, Even if the adhesive layer is adhered to the surface of the substrate opposite to the side on which the adhesive layer is provided (hereinafter sometimes referred to as “back surface of the substrate”), The present invention relates to a surface protective film capable of easily peeling an adhesive layer from the back and capable of unfolding a wound body without difficulty.
The wound body as used in the present invention includes a wound body, and the surface protective film includes a surface protective adhesive film, a surface protective (adhesive) sheet or a surface protective (adhesive) tape.

  Conventionally, surface protective films have been used to protect articles and members. The surface protective film is, for example, a variety of adherends such as synthetic resin plates, decorative plywood, coated steel plates, copper plates, stainless steel plates, etc. Used to prevent scratches. This type of surface protective film has a structure in which an adhesive layer is laminated on a substrate.

  Generally, the surface protective film is industrially manufactured as a wound body obtained by winding a long film in a roll shape, for example. The surface protection film having such a wound body is strongly required to have a small force (developing force) required for unfolding the wound body, that is, to easily rewind the wound body.

  On the other hand, in the surface protective film manufactured by the melt coextrusion method, in order to reduce the developing force, after laminating the base material made of polyethylene and the adhesive layer, the back surface of the base material (adhesive layer lamination of the base material) There has been proposed a method of friction-treating the surface opposite to the side (see Patent Documents 1, 2, or 3).

On the other hand, the outermost layer of a three-layer structure is made of a polyethylene resin, and a surface protective film for automobile coated steel sheets having excellent heat resistance and workability is disclosed by using a polypropylene resin as an intermediate layer (for example, (See Patent Document 4). However, when a soft pressure-sensitive adhesive is used, there is a problem that the developing force becomes high, and in some cases, it cannot be used.
Under these circumstances, there has been a need for research and development of a surface protective film having a small unfolding force even when a soft adhesive that solves the problems of the prior art is used.
Japanese Patent No. 2647189 Japanese Patent No. 2944249 Japanese Patent No. 2625275 Japanese Patent Laid-Open No. 2001-121661

  The object of the present invention is, in view of the state of the prior art described above, even when a soft adhesive is used, it can be used as a wound body, and the surface on the side opposite to the side where the adhesive layer of the substrate is provided It is an object of the present invention to provide a surface protective film that can easily peel off the adhesive layer from the back surface of the substrate even if the adhesive layer is adhered to the substrate, and can unfold the wound body without difficulty.

  In order to achieve the above object, the present inventors have intensively studied a conventional surface protective film, and as a result, the conventional surface protective film is stored and transported as a roll, particularly when a soft adhesive is used. Since the adhesive of the surface protective film of the outer layer tends to stick strongly to the back surface of the base material of the surface protective film of the inner layer, the surface protective film of the outer layer is It does not peel easily from the protective film, and this is difficult to peel due to the strong adhesive energy between the back of the substrate and the adhesive, and by forcibly peeling the adhesive layer from the back of the substrate, The base material was deformed, and it was found that this deformation was due to the consumption of a large amount of energy.

  Therefore, we studied a method to reduce the unfolding force of the wound body by applying a release agent such as a long-chain fatty acid modified product or silicone on the back surface of the base material to make the adhesive layer difficult to stick to the back surface of the base material. However, in this method, it is necessary to perform extra steps such as application of a release agent and drying. Furthermore, in order to reinforce the anchoring property between the back surface of the base material and the release agent, the back surface of the base material also needs to be surface-treated. Therefore, the number of manufacturing steps of the surface protective film increases, resulting in an increase in manufacturing cost.

  On the other hand, while using the surface layer which consists of a specific component as a base material, and performing the process described in patent document 1, patent document 2, or patent document 3, extra processes, such as application | coating of a peeling agent, are carried out. It has been found that a surface film can be obtained that can be easily peeled off from the back surface of the base material and can easily develop the roll.

  As a result of further studies, in a surface protective film in which an adhesive layer is laminated on a single-layer or multilayer polyolefin base material, the surface roughness Ra and the surface protrusion spacing Sm of the adhesive layer made of a specific component are specified. By subjecting the surface of the polyolefin-based substrate on the side where the adhesive layer is not laminated or the outermost layer formed thereon to the range, the substrate can be obtained without performing an extra step such as application of a release agent. It can be easily peeled off from the back surface of the steel sheet, and it has been found that the rolled body can be easily developed, and has found that the present invention has been completed.

That is, according to the first invention of the present invention, a surface protective film in which an adhesive layer containing a rubber-based resin component (X) and a tackifier resin (Y) is laminated on a polyolefin-based substrate, A surface protective film characterized by satisfying the following requirements (a) to (d) is provided.
B) The polyolefin-based substrate is composed of a single layer or multiple layers.
B) The rubber-based resin component (X) is a block copolymer of a styrene polymer block (A) and an olefin polymer block (B), or a random copolymer of a styrene polymer block (A), styrene and an olefin. It consists of a styrene-type elastomer (C) which has a block copolymer with the copolymer block (B2) and / or a hydrogenated product thereof as a main skeleton.
C) The adhesive layer has a surface roughness Ra of 2 to 8 μm and a surface protrusion interval Sm of 25 to 50 μm.
D) The surface of the polyolefin-based substrate on the side where the adhesive layer is not laminated or the outermost layer formed thereon is subjected to friction treatment.

  According to the second invention of the present invention, in the first invention, the rubber resin component (X) is a block copolymer of a styrene polymer block (A) and an isobutylene polymer block (B1). There is provided a surface protective film characterized by being a styrene-based elastomer.

  According to a third aspect of the present invention, there is provided the surface protection film according to the first or second aspect, wherein the friction treatment is friction with a canvas.

  According to a fourth aspect of the present invention, there is provided the surface protective film according to any one of the first to third aspects, wherein the deployment force when the roll is 100 mm wide is 12 N or less. Provided.

  According to the surface protective film of the present invention, the surface roughness Ra of the pressure-sensitive adhesive layer is 2 to 8 μm, the surface protrusion interval Sm is 25 to 50 μm, and the polyolefin on the side where the pressure-sensitive adhesive layer of the surface protective film is not laminated Since the surface or outermost layer of the base material is friction-treated with a canvas or the like, even if the adhesive layer is adhered to the back surface opposite to the side where the adhesive layer is provided, There is an effect that the adhered surface protective film can be easily peeled off from the back surface.

The surface protective film of the present invention is a surface protective film in which a pressure-sensitive adhesive layer containing a rubber-based resin component (X) and a tackifier resin (Y) is laminated on a polyolefin-based substrate. It is characterized by satisfying the requirement (ii).
B) The polyolefin-based substrate is composed of a single layer or multiple layers.
B) The rubber-based resin component (X) is a block copolymer of a styrene polymer block (A) and an olefin polymer block (B), or a random copolymer of a styrene polymer block (A), styrene and an olefin. It consists of a styrene-type elastomer (C) which has a block copolymer with the copolymer block (B2) and / or a hydrogenated product thereof as a main skeleton.
C) The surface roughness Ra of the adhesive layer is 2 to 8 μm, and the surface protrusion interval Sm is adjusted to 25 to 50 μm.
2) The surface of the polyolefin base material on the side where the adhesive layer is not laminated or the outermost layer formed thereon is subjected to a friction treatment.
Hereinafter, the surface protective film of the present invention will be described in detail.

1. Polyolefin-based substrate The polyolefin-based substrate may be composed of a single polyolefin-based substrate layer, or may be a polyolefin-based substrate having a multilayer structure. In the case of multilayering, it is desirable that different functions can be assigned to each polyolefin-based substrate layer, and appropriate mechanical properties and other performances can be easily realized as a surface protective film.
Although the thickness of the polyolefin-based substrate varies depending on the purpose of use, it is usually desirable that the layer is in the range of 20 to 100 μm in the case of a single layer, or in the case of a multilayer, all layers are combined. By making it into the range of 20-100 micrometers, the damage and tear at the time of adhesion | attachment and peeling can be suppressed effectively, and the handleability at the time of adhesion | attachment and peeling can be improved.
The olefin-based substrate itself in the case of a single layer or the polyolefin-based substrate on the side where the adhesive layer in the case of multiple layers is not laminated is referred to as the outermost layer (i), and a layer other than the outermost layer (i) is formed. The layer is also referred to as the inner layer (ii). Each layer will be described.

(1) Outermost layer (i)
In the outermost layer (i), the polyolefin used in the polyolefin-based substrate is composed of a resin component selected from polyethylene, polypropylene, or a mixture thereof. The polyethylene may be any of low density polyethylene (LDPE), linear low density polyethylene (LLDPE), and high density polyethylene (HDPE). As polypropylene, homopolypropylene (homo PP), random polypropylene (random PP), It can be used widely such as block polypropylene (block PP).
In addition, you may mix | blend well-known various additives etc. which are mix | blended normally in this field | area in outermost layer (i).

In the surface protective film of the present invention, it is essential that the surface of the outermost layer (i) opposite to the adhesive layer is subjected to a friction treatment. A friction process is not specifically limited, For example, it can perform by the method described in patent document 1, or the method according to this.
In these, it is preferable that it is the friction by a canvas. Moreover, it is preferable to carry out by buffing.

  This friction treatment is an essential treatment in the present invention, and an effective effect cannot be obtained without the friction treatment. The inventor is still unclear about this mechanism, but it is probably because the crystal structure of the surface has changed due to friction treatment.

(2) Inner layer (ii)
When the polyolefin-based substrate is a multilayer of two or more layers, the inner layer (ii) that is a layer that forms a layer other than the outermost layer (i) that forms the outermost layer on the surface on which the adhesive layer is not formed, The adhesive layer is laminated on one side and is not particularly limited.
In FIG. 1, in the surface protection film of this invention, the structure of an example in case a polyolefin-type base material is a multilayer is shown with a schematic cross section. As such an inner layer (ii), it is possible to use a general polyolefin such as polypropylene or polyethylene, or a mixture of polyolefin and an olefin elastomer as the polyolefin.
In addition, arbitrary thickness can be set for the said inner layer (ii) by a use application.

  For the inner layer (ii), a recycled product of the surface protective film may be added to such an extent that physical properties are not affected. The recycled product may be a collected product of a used surface protection film, or an ear end slit product during production of the surface protection film. For example, the recycled product of the surface protective film is suitably about 30% or less, more preferably about 20% or less with respect to the total weight of the inner layer. When the content of the recycled product is excessively large, components other than the polyolefin are included in a large amount, and the desired effect may not be sufficiently exhibited. On the other hand, by using recycled products, production costs can be reduced and interlayer adhesion can be further increased.

In this invention, you may mix | blend well-known various additives normally mix | blended in this field | area in the inner layer (ii). Examples of such additives include lubricants, antistatic agents, rust preventives, pigments, and the like, in addition to additives to be added to the adhesive layer described below.
In particular, in the case of a surface protective film used for applications that are exposed to ultraviolet rays, a light-resistant agent is blended in the inner layer (ii).
As the light-resistant agent blended in the inner layer (ii), an ultraviolet shielding agent and / or an ultraviolet stabilizer is preferably used.
Examples of the ultraviolet shielding agent include inorganic pigments such as titanium oxide, zinc oxide, calcium carbonate, and carbon black. These may be used alone, or may be used by blending a plurality of them. Of these, titanium oxide is particularly preferably used because of its excellent ultraviolet shielding properties.
Examples of the ultraviolet stabilizer include salicylic acid-based, benzophenone-based, benzotriazole-based, cyanoacrylate-based ultraviolet absorbers, and hindered amine-based light stabilizers. Only 1 type may be used for these and 2 or more types may be used together.

The polyolefin base material composed of the outermost layer (i) and the inner layer (ii) described above preferably has a tensile modulus of 400 MPa or more, more preferably 500 MPa or more. Thereby, even if a long surface protection film is wound in a roll shape to form a wound body, the substrate is prevented from being deformed by the adhesive force of the adhesive layer when the wound body is developed. be able to. Therefore, energy consumed for deformation of the base material can be reduced, so that the outermost surface protective film can be easily peeled off from the inner surface protective film, and the wound body can be unreasonably developed.
On the other hand, when the polyolefin-based substrate is a single layer, the tensile elastic modulus is preferably 400 MPa or more, more preferably 500 MPa or more, for the same reason as in the case of a multilayer.
In addition, it is preferable to use a crystal nucleating agent as a material constituting the outermost layer (i) and the inner layer (ii) to further improve the tensile elastic modulus. Thereby, a deformation | transformation of a base material can be suppressed more.

2. Adhesive layer In this invention, an adhesive layer consists of an adhesive composition which has a rubber-type resin component as a main component. Specifically, it is necessary to contain the rubber-based resin component (X) and the tackifier resin (Y).
The pressure-sensitive adhesive layer of the surface protective film according to the present invention is laminated on one side of the polyolefin base material. This adhesion layer contains the rubber-type resin component (X) which consists of a styrene-type elastomer (C), and tackifying resin (Y). Hereinafter, the characteristics of the rubber-based resin component (X) and the tackifier resin (Y), other components, and the adhesive layer will be described.

(1) Rubber resin component (X)
An example of the styrene elastomer (C) as the rubber resin component (X) is a block copolymer of a styrene polymer block (A) and an olefin polymer block (B). Another example is a block copolymer of a styrene polymer block (A) and a random copolymer block (B2) of styrene and olefin. Furthermore, another example has a hydrogenated product of these copolymers as a main skeleton.

Here, the olefin polymer block (B) may be an isobutylene polymer block (B1). The random copolymer block (B2) of styrene and olefin is preferably a random copolymer block (B2) of styrene and isobutylene for reasons of durability.
In other words, the styrene elastomer (C) is preferably a styrene elastomer of the following 1), 2) and 3).

1) A styrene elastomer having a main skeleton of a block copolymer of a styrene polymer block (A) and an isobutylene polymer block (B1). The styrene-based elastomer is not particularly limited as long as the (A)-(B1) block copolymer is a main skeleton. For example, A-B1, A-B1-A, (A-B1) _n or (A _-B1) copolymers thereof represented by like _n X. X is a residue derived from a coupling agent.

2) A styrene elastomer having a main copolymer of a block copolymer comprising a styrene polymer block (A) and a random copolymer block (B2) of styrene and isobutylene. Examples of such a styrene elastomer include the following (2-1) to (2-4).

(2-1) Block (A) and block (B2) combined: A-B2 block copolymer (2-2) Containing taper block (D) in which styrene of styrene and isobutylene gradually increases: A-B2-D block copolymer (2-3) Including styrenic polymer block (A) instead of taper block (D): A-B2-A block copolymer (2-4) ( 2-1) to (2-3) repetition and those in which these are bonded at an arbitrary ratio: (A-B2) _n , (A-B2) _n X, (A-B2-D) _n X, (A -B2-A) _n X and the like.

  In the styrene-based elastomer (C) of 2) above, the content ratio of styrene as a component and isobutylene is preferably in the range of 5 to 95 to 60 to 40, more preferably 7 to 93 to 40, by weight ratio. Pair 60. When the content of styrene is less than 5% by weight, the cohesive strength of the pressure-sensitive adhesive is lowered, and there is a possibility that adhesive residue may be generated on the adherend when it is peeled off from the adherend. It may be insufficient and sticking to the adherend may be difficult.

In the styrene-based elastomer (C) of 2), in the configuration including the block (D), the styrene content in the block (A) and the styrene content in the block (D) in all monomer configurations constituting the styrene-based elastomer The total of the styrene content ratio, which is the total amount, is preferably 3 to 50% by weight, more preferably 5 to 40% by weight, and still more preferably 5 to 25% by weight. When the total content of styrene in the block (A) and the block (D) is less than 3% by weight in the total monomers, the cohesive force of the pressure-sensitive adhesive is reduced, and there is a possibility that an adhesive residue may be generated upon peeling from the adherend. If it exceeds 50% by weight, the adhesive strength of the pressure-sensitive adhesive is insufficient, which may make it difficult to attach to the adherend. The proportion of styrene in the block (A) in the total monomers constituting the styrene elastomer (C) is preferably 3% by weight or more, more preferably 3 to 20% by weight.
In addition, the styrene-based elastomer (C) of the present invention may be partially modified or the like for the purpose of improving the adhesion with the substrate.

  The polystyrene-equivalent weight average molecular weight measured by GPC of the styrene elastomer (C) is preferably in the range of 30,000 to 400,000, more preferably 50,000 to 200,000. If it is less than 30000, the cohesive force of the pressure-sensitive adhesive will be reduced, and adhesive residue may be generated upon peeling from the adherend. If it exceeds 400000, the adhesive force will be insufficient and the fluidity tends to deteriorate.

(2) Tackifying resin (Y)
In addition to the rubber-based resin component (X) composed of the styrene-based elastomer (C), the pressure-sensitive adhesive layer further contains a tackifier resin (Y).
Specific tackifying resins include, for example, aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, terpene resins, terpene / phenol resins, alkyl / phenol resins, coumarone / indene resins. Examples thereof include resins, rosin resins, paraffinic process oils, naphthenic process oils, aromatic process oils, castor oil, tall oil, natural oils, and liquid polyisobutylene resins. Specifically, Arakawa Chemical Co., Ltd. as an alicyclic petroleum resin, product name: Alcon, Yashara Chemical Co., Ltd. as a terpene resin, Product name: Clearon, Idemitsu Kosan Co., Ltd. as a paraffinic process oil, Product name: Diana Process Oil Examples of the liquid polyisobutylene resin include BASF Corporation, trade name: Glysopearl. These may be used independently and 2 or more types may be used together.

  It is preferable that the said tackifying resin is mix | blended in 5 to 70 weight part with respect to 100 weight part of styrene-type elastomer (C), More preferably, it is 20 to 50 weight part. If it is less than 5 parts by weight, the shear storage elastic modulus described below may be too high, and the adhesive force to the adherend may be insufficient. If it exceeds 70 parts by weight, the cohesive force of the pressure-sensitive adhesive is insufficient, and after use as a surface protective film, it may be difficult to peel off from the adherend, and there is a possibility that an adhesive residue may be generated upon peeling.

(3) Other components In the pressure-sensitive adhesive layer of the surface protective film according to the present invention, an ultraviolet absorber, a light stabilizer, an antioxidant, an adhesion progressing inhibitor, as long as the adhesive performance is not impaired, Softeners, fillers and the like may be added.

  The ultraviolet absorber is not particularly limited, and examples thereof include commonly used ones such as salicylic acid series, benzophenone series, benzotriazole series, and cyanoacrylate series. Examples of the light stabilizer include hindered amine compounds. The antioxidant is not particularly limited, and examples thereof include commonly used ones such as phenolic (monophenolic, bisphenolic, and high-molecular phenolic), sulfur, and phosphorus. Examples of the anti-adhesion progress agent include fatty acid amides, polyethyleneimine long-chain alkyl grafts, soybean oil-modified alkyd resins (for example, Arakawa Chemical Co., Ltd., trade name “Arachid 251”, etc.), tall oil-modified alkyd resins (for example, Arakawa Chemical Co., Ltd., trade name “Arachid 6300”, etc.).

(4) Properties of the pressure-sensitive adhesive layer The pressure-sensitive adhesive layer of the present invention has a surface roughness Ra of 2 to 8 μm, preferably 3 to 7 μm, and a surface protrusion interval Sm of 25 to 50 μm, preferably 35 to 35 μm. 45 μm. If Ra is less than 2 μm, even if Sm is within the target range, it will be difficult to unfold the wound body. If Ra exceeds 8 μm, the adhesive strength will be weakened when affixed to the adherend. Floating occurs after attaching. Moreover, when Sm is less than 25 μm, the effect of reducing the developing force is thin, and when it exceeds 45 μm, the adhesive force to the adherend is hardly expressed and floating occurs.
Ra and Sm are values measured by the method described in the examples.

  The pressure-sensitive adhesive having Ra and Sm can be applied with a pressure-sensitive adhesive solution on a film having a shaping roll or an uneven shape.

Further, the adhesive layer preferably has a shear storage elastic modulus at a frequency of 10 Hz of 1 × 10 ⁶ Pa or less at 23 ° C. When the shear storage elastic modulus is outside this range, the surface protective film may be peeled off from the adherend during transportation due to insufficient adhesive force, and workability in the peeling process may be deteriorated.
The shear storage elastic modulus was measured in the range of −50 ° C. to + 150 ° C. at a frequency of 10 Hz and a temperature increase rate of 6 ° C./min with a dynamic viscoelastic spectrum measurement device (IT Measurement Control Co., Ltd., product number: DVA200). The value obtained at 23 ° C.

  Although the thickness of an adhesion layer is not specifically limited, The range of 3-50 micrometers is desirable. When the thickness is less than 3 μm, the adhesive strength may be insufficient, and when it exceeds 50 μm, the cost is disadvantageous.

3. Method for producing surface protective film The method for producing the surface protective film of the present invention is not particularly limited. For example, the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer and the composition constituting the polyolefin-based substrate are coextruded. For example, a method of laminating and integrating, or a method of laminating and integrating a pressure-sensitive adhesive composition on a film-formed polyolefin substrate, and the like.

  As a method of laminating and integrating the polyolefin base material and the pressure-sensitive adhesive composition by coextrusion, a known method such as an inflation method or a T-die method can be used. As a method for laminating the pressure-sensitive adhesive composition on a polyolefin-based substrate, a solution coating method for coating a pressure-sensitive adhesive solution, a dry lamination method, an extrusion coating method using a T-die, or the like is used. Among these, a co-extrusion method using a T-die is preferable because quality can be improved and production can be made economically. Further, when the solution coating method is performed, in order to increase the bonding strength between the base material layer and the pressure-sensitive adhesive layer, it is preferable to apply a primer to the polyolefin base material in advance to perform surface treatment.

  In addition, for a polyolefin-based substrate having a multilayer structure, a method of coextruding the composition constituting each polyolefin-based substrate layer together with the above-mentioned pressure-sensitive adhesive composition and laminating and integrating, or a polyolefin-based substrate having a multilayer structure in advance After preparing the above, a method of coating the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer on the polyolefin-based substrate may be used.

4). Development force of surface protection film The surface protection film according to the present invention preferably has a force (deployment force) of 12 N or less when a 100 mm-wide wound body is rewound at a speed of 0.3 m / min. More preferably, it is 10 N or less. When it exceeds 12N, when the width of the wound body exceeds 1000 mm, the drawing workability may be deteriorated.

Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples.
The evaluation methods and resin materials used in the examples are as follows.

1. Evaluation method (1) Surface roughness (Ra, Sm)
Measurements were made using the following equipment and conditions.
Device name: Surfcom 1400D (manufactured by Tokyo Seimitsu)
Probe: 2 μmR Diamond measuring force: 0.75 mN
Measurement length: 2.4mm
(2) Initial adhesive strength The obtained surface protective film was coated with an automotive coated steel sheet (steel having an alkyd-melamine coating film having a glass transition point of 60 ° C., surface gloss) in an environment of room temperature 23 ° C. and relative humidity 65%. 80%), each using a 2 kg pressure-bonded rubber roller, and affixed at a speed of 300 mm / min, left in that state for 30 minutes, and in accordance with JIS Z0237, the 180-degree peel strength at a width of 25 mm is 300 mm / min. Measured at the speed of The peel strength measured in this manner was taken as the initial adhesive strength.
(3) Initial peeling force The obtained surface protective film was coated with an automotive coated steel sheet (steel sheet having an alkyd-melamine coating film having a glass transition point of 60 ° C., surface gloss) in an environment of room temperature 23 ° C. and relative humidity 65%. 80%), each using a 2 kg pressure-bonded rubber roller, and affixed at a speed of 300 mm / min, left in that state for 30 minutes, and in accordance with JIS Z0237, the 180-degree peel strength at 25 mm width is 30 m / min. Measured at the speed of The peel strength measured in this way was taken as the initial peel force.
(4) Adhesive strength after 1 week at 50 ° C. The obtained surface protective film was coated with an automotive coated steel sheet (with an alkyd-melamine coating film having a glass transition point of 60 ° C.) in an environment at room temperature of 23 ° C. and relative humidity of 65%. Steel sheets, surface gloss 80%), each using a 2 kg pressure-bonded rubber roller, affixed at a speed of 300 mm / min. The 180 degree peel strength at 25 mm width was measured at a speed of 30 m / min. The peel strength measured in this way was defined as the adhesive strength after one week at 50 ° C.
(5) Unfolding force The unfolding force was determined by measuring the force required when unwinding the rolls of 100 mm width of each surface protective film of Examples and Comparative Examples at a speed of 0.3 m / min and 20 m / min. .
(6) Floating The sample before adhesion measurement obtained in (4) above was visually observed for the presence or absence of floating.

2. Materials used (1) Rubber resin component (X) (styrene elastomer)
SIBS; manufactured by Kaneka Corporation, product number: Shibster 102T, block copolymer of styrene and isobutylene (Mw: about 100,000, styrene content ratio in all monomers: 14% by weight)
SEBS; manufactured by Asahi Kasei Co., Ltd., product number: Tuftec H1052, block copolymer of styrene and ethylene / butylene (styrene content in all monomers: 20% by weight)
(2) Tackifying resin (Y)
PA: Paraffinic process oil manufactured by Kobe Oil Chemical Co., Ltd., trade name: SYNTAC PA95 (weight average molecular weight 400)
Alcon P125; hydrogenated petroleum resin manufactured by Arakawa Chemical Co., Ltd. (3) Polyolefin-based material FL4; Polypropylene M12 manufactured by Nippon Polypro Co., Ltd. Polyethylene (LDPE) manufactured by Prime Polymer Co., Ltd.
QT4125: Asahi Kasei Polyethylene (HDPE)

Example 1
A pressure-sensitive adhesive composition containing 100 parts by weight of SIBS (SIBS manufactured by Kaneka Corporation, product number: Shibster 102T) as a styrene-based elastomer and 20 parts by weight of paraffinic process oil (PA95) as a tackifying resin is used for the adhesive layer. , M12 is used for the outermost layer, FL4 is used for the inner layer, and co-extrusion is performed at T = 220 ° C. by the T-die method. A surface protective film in which layers were laminated was obtained.
The surface of the outermost layer of the obtained surface protective film was polished by buffing with a buff using a canvas, and then wound on a paper core having an inner diameter of 3 inches to obtain a wound body of the surface protective film. Table 1 shows the evaluation results of the obtained surface protective film.

(Examples 2-3 and Comparative Examples 1-4)
A surface protective film was obtained in the same manner as in Example 1 except that the types and blending ratios of the rubber-based resin component and tackifying resin used and the presence or absence of friction treatment were changed as shown in Table 1. Table 1 shows the evaluation results of the obtained surface protective film.

  As a result of comparing the examples and comparative examples that do not satisfy the invention specific items from the evaluation results of Table 1, the surface protective films according to Examples 1 to 3 are all good in adhesive force, peeling force, and deployment force, Even when a soft adhesive is used, it can be a wound body or the like, and even if the adhesive layer is adhered to the surface of the substrate opposite to the side where the adhesive layer is provided, the adhesive is adhered from the back of the substrate. The layer could be easily peeled off, and it was confirmed that the surface protective film was able to unfold the wound body without difficulty.

  The surface protective film of the present invention can be a wound body even when a soft adhesive is used, and the adhesive layer is adhered to the surface of the substrate opposite to the side where the adhesive layer is provided. In particular, since it is a surface protective film that can easily peel the adhesive layer from the back surface of the base material and can unfold the wound body without difficulty, the adhesion of dust to the surface of the adherend and the adherend It is suitable as a surface protective film provided as a roll used to prevent scratches on the surface.

In the surface protection film of this invention, it is a schematic cross section which shows a structure of an example in case a polyolefin-type base material is a multilayer.

Claims (4)

A surface protective film in which a pressure-sensitive adhesive layer containing a rubber-based resin component (X) and a tackifier resin (Y) is laminated on a polyolefin-based substrate, and satisfies the following requirements (a) to (d): Characteristic surface protective film.
B) The polyolefin-based substrate is composed of a single layer or multiple layers.
B) The rubber-based resin component (X) is a block copolymer of a styrene polymer block (A) and an olefin polymer block (B), or a random copolymer of a styrene polymer block (A), styrene and an olefin. It consists of a styrene-type elastomer (C) which has a block copolymer with the copolymer block (B2) and / or a hydrogenated product thereof as a main skeleton.
C) The adhesive layer has a surface roughness Ra of 2 to 8 μm and a surface protrusion interval Sm of 25 to 50 μm.
D) The surface of the polyolefin-based substrate on the side where the adhesive layer is not laminated or the outermost layer formed thereon is subjected to friction treatment.   The surface of claim 1, wherein the rubber resin component (X) is a styrene elastomer comprising a block copolymer of a styrene polymer block (A) and an isobutylene polymer block (B1). Protective film.   The surface protection film according to claim 1, wherein the friction treatment is friction by a canvas.   The surface protection film according to any one of claims 1 to 3, wherein a deployment force when the roll is 100 mm wide is 12 N or less.

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